The role of the refrigerant separation tank in the design of LNG cryogenic tanks

In the design of LNG (liquefied natural gas) cryogenic tanks, a refrigerant separation tank is typically used to separate the gaseous and liquid forms of the refrigerant. During the cooling and liquefaction of LNG, it is necessary to use a refrigeration system to lower the temperature of the natural gas below its liquefaction point. This refrigeration cycle typically uses one or more refrigerants to absorb heat from natural gas through evaporation and compression cycles. The main functions of the refrigerant separation tank are as follows: 1. Separating the gas-liquid mixture: After passing through the throttle valve (the throttling process usually results in a decrease in pressure and temperature), the refrigerant may partially evaporate, resulting in a gas-liquid two-phase mixture. The refrigerant separation tank is designed to be large enough to provide sufficient residence time, allowing the gas-phase and liquid-phase refrigerants to separate thoroughly. 2. Ensure the efficiency of the refrigeration cycle: By removing the gaseous refrigerant from the mixture, it is possible to ensure that liquid refrigerant enters the evaporator, thereby improving evaporation efficiency and ensuring the stability of the refrigeration cycle. 3. Preventing compressor liquid slugging: The refrigerant separator tank also protects the compressor from damage caused by liquid refrigerant. If liquid refrigerant enters the compressor, it can cause liquid slugging, affecting the normal operation of the compressor and even damaging it. 4. Storage regulation: The separation tank can also serve as a storage medium for the refrigerant; by adjusting the amount of refrigerant stored in it, it is possible to meet the requirements of the refrigeration system under different operating conditions. In LNG cryogenic tanks, the throttling process may be designed with throttle valves in upper, middle, and lower sections, allowing for more precise control over temperature and pressure changes. Corresponding separation tanks are thus installed after each section to ensure effective separation under different conditions and pressures. .